DE 38 31 676 C1, for example, has disclosed a hydrostatic profiled rail guide, in which a guide carriage is mounted hydrostatically on a guide rail. The guide rail is provided with a center face which extends along its longitudinal axis and with two upper bearing faces which are arranged on both longitudinal sides of the center face and are arranged such that they are inclined with respect to said center face. Below each upper bearing face, a lower bearing face is provided which is arranged such that it is inclined with respect to said upper bearing face and with respect to the center face. As viewed in cross section through the profiled rail guide, a triangle is defined by an imaginary first parallel straight line to the center face, by an imaginary second parallel straight line to the upper bearing face and by an imaginary third parallel straight line to the lower bearing face. In this triangle, first and the second straight lines. Furthermore, an angle γ is formed in this triangle between the first and the third straight lines.
Two emergency running faces which delimit an angle β of at most 90° with the lower bearing faces of the head region are provided in the foot region of the guide rail on its two longitudinal sides below said two upper and lower bearing faces which are provided in the head region of the guide rail.
The guide carriage which is placed onto the guide rail is likewise provided with upper and lower bearing faces which interact with the upper and lower bearing faces of the guide rail. Pressure pockets are formed between the respective bearing faces of the guide rail and the guide carriage, in which pressure pockets a hydrostatic pressure can be built up. The hydrostatic pressure makes it possible to mount the guide carriage satisfactorily on the guide rail.
The back of the guide carriage is usually provided with a clamping face for clamping a machine part, for example. The machine part can be a tool or any desired other component. Said machine parts as a rule have a flat support face for resting on the clamping face of the back.
The possible applications of hydrostatic profiled rail guides of this type can be restricted by the fact that the limbs of the guide carriage can bend apart under a prevailing load. In this case, the pressure cushions which are built up in the pressure pockets cannot be maintained in some circumstances, with the result that satisfactory operation of the hydrostatic profiled rail guide is not ensured. Problems of this type can be eliminated, for example, by increasing the outer proportions of the guide carriage, with the result that the limbs of the guide carriage become more rigid. However, modifications of this type have the disadvantage that it is not possible to exchange profiled rail roller guides for hydrostatic profiled rail guides. The outer geometry of profiled rail roller guides is stipulated according to DIN 645-1. Known hydrostatic profiled rail guides cannot be used as a replacement for customary profiled rail roller guides, since a modification of the outer proportions is required in the case of comparable loadings of said hydrostatic profiled rail guides to ensure satisfactory operation, with the result that DIN 645-1 is not complied with.
It is an object of the present invention to specify a hydrostatic profiled rail guide in which proper operation is ensured.
According to the invention, this object is achieved in that the clamping face is arched concavely as viewed in the longitudinal direction of the guide rail. If the machine part is clamped onto this clamping face, it is tightened, for example, with screws. Said concavely shaped clamping face can be flattened during this tightening of the machine part, the back itself bending about a bending axis which is parallel to the longitudinal center axis of the guide carriage during this flattening, the free ends of the two limbs pivoting somewhat toward one another. When the machine part is bolted fixedly onto the clamping face of the guide carriage, a clearance between the guide rail and the guide carriage in the region of the bearing faces can be very small, for example from 5 to 10 μm. If this hydrostatic profiled rail guide is then pressurized, however, for example 100 bar, compressive forces which result in the two limbs of the guide carriage bending counter to their prestress act between the bearing faces of the guide rail and of the guide carriage. During this bending of the two limbs in the opposite direction, an ideal clearance which can be, for example, 25 μm is then set. That means that the desired clearances can be maintained under the provided operating loads between the bearing faces of the guide rail and of the guide carriage, even in the case of unfavorable loading of the hydrostatic profiled rail guide. No enlarged clearances are produced, with the result that no undesirably high volumetric flow of hydraulic fluid enters. This advantageous effect is made possible by the concavely shaped clamping face of the guide carriage, which concavely shaped clamping face makes a prestress which is introduced in a targeted manner possible in the back of the guide carriage, which prestress counteracts undesired contact of the limbs of the guide carriage. Defined bending of the back about an imaginary bending axis along the guide rail is possible by way of the profiled rail guide according to the invention.
The invention can also be described in other words by the fact that the clamping face is provided on both sides of the longitudinal center axis of the guide carriage with one clamping bar or clamping edge each, between which the clamping face is recessed. If the machine part is placed onto the guide carriage as described above, a spacing is formed between the flat support face of the machine part and the recessed clamping face of the back. If the machine part is then clamped to the guide carriage as shown above, the back is pulled with its clamping face in the direction of the flat support face of the machine part. As described above, the two limbs of the guide carriage pivot toward one another during this flattening of the concave or recessed clamping face of the back.
The guide carriage is preferably provided along its longitudinal center axis with a plurality of threaded holes which are arranged one behind another or with threaded shanks which protrude from the plane of the clamping face, in order to screw the machine part to the guide carriage. The screw forces which act on the screw connection act on the two limbs of the guide carriage with a lever arm which corresponds precisely to the spacing between the clamping edge and the longitudinal center axis.
It can be expedient for the proper design of the hydrostatic profiled rail guide according to the invention to define a first plane E1, in which the two clamping bars or edges are arranged. The recessed clamping face then lies in a plane E2 which is spaced apart from the plane E1. In the case of a concavely shaped clamping face, said concave clamping face is tangent to said plane E2. The spacing between said two planes E1 and E2 is then set in such a way that said spacing is reset to zero during clamping of the machine part onto the guide carriage. A stop size can therefore be defined by way of the set spacing h, with the result that the gap size between the bearing faces of the guide rail and of the guide carriage has a provided low spacing after this stop is reached. The desired clearance between said bearing faces is set only after the hydrostatic profiled rail guide according to the invention is pressurized.